[Sparc] EXPENSIVE_CHECKS now passes all machine verifier errors (PR27461)

[RKSimon]

Summary

Now that D51487 has landed, the last machine verifier tests that failed EXPENSIVE_CHECKS builds have now been fixed/removed, so we can remove @MatzeB 's isMachineVerifierClean() hack for sparc targets.

[MatzeB]

yay \o/ LGTM

llvm/trunk/lib/Target/Sparc/SparcTargetMachine.h

public:
   const SparcSubtarget *getSubtargetImpl() const { return &Subtarget; }
   const SparcSubtarget *getSubtargetImpl(const Function &) const override;
 
   // Pass Pipeline Configuration
   TargetPassConfig *createPassConfig(PassManagerBase &PM) override;
   TargetLoweringObjectFile *getObjFileLowering() const override {
     return TLOF.get();
   }
-
-  bool isMachineVerifierClean() const override {
-    return false;
-  }
 };
 
 /// Sparc 32-bit target machine
 ///
 class SparcV8TargetMachine : public SparcTargetMachine {
   virtual void anchor();
 public:
   SparcV8TargetMachine(const Target &T, const Triple &TT, StringRef CPU,